Total marine fisheries extractions by country in the Baltic Sea

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170 Total marine fisheries extractions by country in the Baltic Sea: 1950-present, Rossing, Booth and Zeller values to represent the rates of unreported landings for ‗others‘ (Table 5). These rates were applied to total landings (ICES landings statistics + adjustments) in 1993, 1994, and 2007. Linear interpolations were performed between 1990 (0%) and our first anchor point in 1993 (15.4%), and in all other intervening years (Table 5). Discards Discards were estimated for four separate categories: i) underwater discards (mortality caused by deployed fishing gear); ii) ghostfishing (a result of entrapment in lost fishing gear); iii) boat-based discards (usually a result of fishers‘ selective behaviors onboard); and iv) seal-damaged discards. In Poland however, only categories the first three categories were applicable. Discards were estimated by applying annual rates (%) to estimates of our total annual landings (the sum of ICES landings statistics, and adjustments, and unreported landings) of each of the applicable taxa. Underwater discards: Underwater discards were estimated only for herring and sprat since these taxa are the main pelagics targeted by trawl (Zeller et al., this volume). In the Baltic Sea, herring and sprat are targeted by the same trawl fleet. Thus, the pelagic trawl fishery is inherently mixed, and uncertainty exists in species composition of landings data (ICES, 2009b). It is also known that landings statistics often reflect only the targeted species (HELCOM, 2009). Thus, information attained regarding underwater discards was applied to landings of both herring and sprat. Rahikainen et al. (2004) related underwater discard amounts to observed catches of herring in the trawl fishery. We transformed these data into an approximate underwater discard rate of 9% of reported landings caught by trawl (Zeller et al., this volume). In Poland, landings of herring and sprat were not recorded by gear type, so we reduced the underwater discard rate to 5% to account for any other gear types used, and to remain conservative in our estimate. Thus, a rate of 5% was applied to herring and sprat landings (i.e. ICES landings statistics, adjustments and unreported landings) for all years between 1950 and 2007. Ghostfishing: In a recent FAO report, lost and discarded fish gear were reported to contribute to approximately 10% of marine litter globally; resulting in increasingly significant threats to fish stocks (Macfadyen et al., 2009). Brown et al. (2005) reported that during a 28 month study period, between 3 and 906 t of cod were caught by lost nets (based on data from Tschernij and Larsson, 2003). When compared to the total reported or landed catch in the same area, during the same time period, catches by lost gear were equivalent to approximately 0.01-3.2 % of the total catch of cod (Brown et al., 2005). We assumed lost gear has similar effects on all species, excluding pelagics (herring and sprat), and applied the average (1.65%) from Brown et al. (2005) to landings from 1950 to 2007. Boat-based discards: As part of the former eastern bloc, we assumed that Polish fishers did not engage in discarding associated with economic and quota incentives prior to the early 1990s. More indirect forms of discarding would have occurred however, due to the inherent effects of fishing gear on catch and we consider that fish unfit for landing, and inedible or unpalatable fauna would likely have been discarded at sea. Due to the absence of any specific data to account for these types of discards, we assigned a conservative rate of 2% to all species from 1950-1990 excluding herring and sprat (Zeller et al., this volume). From 1993-2007, we derived annual boat-based discard rates for cod and Table 6. Anchor points (%) used for estimating boat based discards for cod and salmon from 1950- 2007 based on sources (Tables 2.4.1, 2.4.5b and 2.4.20 in ICES, 2008a; Table 2.4.5b in ICES, 2007). Dashed lines (-) indicate years when linear interpolations were used. Year Eastern cod Western cod Salmon 1950-1989 2.0 2.0 2.0 1990-1992 - - - 1993 3.4 14.5 14.1 1994 2.1 10.6 12.9 1995 1.7 11.3 13.9 1996 1.2 15.7 15.1 1997 3.9 10.0 14.9 1998 3.4 17.3 14.2 1999 2.5 11.6 14.8 2000 6.8 12.5 10.3 2001 3.2 11.2 15.0 2002 2.2 10.4 15.8 2003 2.8 15.8 15.4 2004 1.8 10.1 15.6 2005 3.0 18.6 15.2 2006 13.2 8.6 17.4 2007 11.3 8.3 14.2 salmon based on default methods described in Zeller et al. (this volume). Default discard rates were also used for flatfishes and ‗others‘ (Zeller et al., this volume; Anon., 2006a), except whiting for which speciesspecific discard data were available (Anon., 2006a).
Total marine fisheries extractions by country in the Baltic Sea: 1950-present, Rossing, Booth and Zeller 171 We derived annual discard rates beginning in 1993 for eastern cod, western cod, and salmon. As country specific discard data were unavailable, we used our default and assumption-based approach (Zeller et al., this volume). These methods produced annual Baltic-wide discard rates (%) for eastern cod, western cod, and salmon (Table 6), which were applied to the sum of ICES landings statistics, plus adjustments, plus unreported landings to estimate the total boat-based discards (t) for these species. To estimate discards for the remaining taxa in Poland we relied on information from a study conducted by the Danish National Institute of Aquatic Resources (Anon., 2006a). We transformed the tonnages of discards reported for the Danish fleet over one year period to a percentage of Denmark‘s reported landings for the respective taxa. Discard rates were assigned annually as fixed rates (1993-2007) to the sum of ICES landings statistics, adjustments, and unreported landings. A linear interpolation was done between 1990 (0%) and our first anchor point in 1993, to phase in the behavior of boat-based discarding. We applied the following rates to the respective taxa in Poland: dab (33%), plaice (34%), flounder (48%), turbot (38%), brill (38%), whiting (38%) and ‗others‘ (6.24%; Zeller et al., this volume). Table 7. The number of Polish recreational fishers from 1986-2007 in Poland. Interpolated values indicated by dashed (-) line. Data source: (Anon., 1989). Year Polish fishers 1986 0 1987-1998 - 1999 6,300 2000 13,700 2001 16,100 2002 21,500 2003 26,500 2004 31,500 2005 38,000 2006 79,043 2007 79,043 a a 2006 value carried forward. Recreational catches Sport and recreational fishing in Poland began in the late 1980s (Radtke and Dabrowski, 2007). Recreational catches were estimated for Poland by using a combination of Polish data regarding the number of recreational fishers between 1999 and 2007 (Anon., 1989), with taxon-specific, per capita catch data for Germany in 2005-2006 (Anon., 2007a) Recreational catch rates were presented by (1999) for cod, herring and flounder. To remain conservative, we applied half of the German recreational catch rates (Table 8) to the estimated number of recreational fishers in Poland (Table 7), to estimate recreational catches of cod, herring and flounder from 1986-2007. Table 8. Recreational catch rates (t∙fisher -1 ) by species used to estimate Poland‘s recreational catches (Anon., 2007). Common name Catch rate (t∙fisher -1 ) Cod 0.011746 Herring 0.000251 Flounder 0.000912 RESULTS Our results estimate the total marine fisheries catches in Poland from 1950 to 2007. The reconstruction of Poland‘s catches uses ICES landings statistics as baseline data to represent all reported landings during the study period (1950-2007). To reconstruct Poland‘s total catches we estimated four components of Illegal, Unreported and Unallocated (IUU) catches to supplement our baseline data from ICES. The first step, which we termed ‘adjustments’, sought to correct any misreported or missing landings from the ICES data. Reported landings were adjusted both negatively and positively using ICES stock assessment working group data (ICES, 2008a; ICES, 2007; ICES, 2008b) as well as national data from the Polish Maritime Fish Industry (Anon., 1989). Secondly, we estimated ‗unreported landings’ as a proportion of ICES landings statistics plus adjustments. ‘Discard’ rates were then estimated and applied to our total reconstructed landings (ICES landings statistics + adjustments + unreported landings). Finally, ‗recreational catches’ were estimated beginning in the 1990s when Poland became indepenedent with the disintegration of the former Eastern Bloc. The sum total of ICES landings statistics, adjustments, unreported landings, and recreational catches represents an estimate of the total fisheries catches from the Baltic Sea by Poland for the period 1950-2007 (see Appendix Tables B1-B7 for complete time series data on all additions to taxonomic catch data, by catch component). ICES landings statistics The ICES landings statistics database presented a total of approximately 7 million tonnes for all species landed from all fishing areas by Poland within the Baltic Sea for the period 1950-2007 (Figure 2). The
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Total marine fisheries extractions by country in the Baltic Sea

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